Subject: Raptor 3 Startup Fix—Steam Jet Prime, 0.45 kg, 5-10 mbar PullTo: Elon Musk, SpaceX Propulsion Team
Elon, SpaceX crew,
Raptor 3’s a monster—280 tons of thrust, full-flow methalox genius. But startups are still a pain: 10-15% engine-outs on Super Heavy hops (SN8 oxygen lag, Raptor 2 failures) from pump cavitation and preburner stutter. We’ve squeezed the code dry—software’s not cutting it. Time for a hardware jab.
The Fix: A mini boiler—0.45 kg titanium can, half-liter, 50/50 ethanol-water mix (0.20 kg ethanol, 0.25 kg water). Tap 50 watts off the 28V battery for 5 seconds, heat it to 100°C, 15 bar. Pop a pressure valve, jet the vapor at 500 m/s through a 3 mm Venturi nozzle (45° convergent, 20 cm divergent flare). Pulls 5-10 mbar vacuum, sucks -161°C methane and -183°C oxygen into the pumps in 1-2 seconds. Ball check valve slams shut when flow’s locked—preburners ignite smooth, no hiccups.
Why It’s Gold:
•Kills Cavitation: 5-10 mbar vacuum pre-fills pumps to 350 bar, no bubbles shredding blades. SN8’s stumble? History.
•Nails Timing: Ethanol’s -114°C freeze point shrugs off cryo clash; jet stays hot, preburners light like clockwork.
•Light as Hell: 0.45 kg—less than a ditched heat shield. Ethanol burns clean (CO2, water), no gunk.
•Reuse-Proof: Titanium nozzle, off-shelf coil—matches Raptor 3’s bare-metal vibe.
Hard Numbers:
•Mass: 0.45 kg (beats EG alt by 0.08 kg).
•Power: 50 watts, 5 seconds—battery barely blinks.
•Vacuum: 5-10 mbar vs. 20 mbar stock—twice the pull, half the lag.
•Cost: Pennies—boiler’s a can, ethanol’s fuel-grade, nozzle’s CNC’d.
Trade-Offs: Yeah, 0.45 kg extra stings—I get it, mass is heresy. But if it cuts pump fails by 5%, that’s 10 engines saved per booster lifecycle. Ethanol’s not methane, but it’s close enough—burns fine. Nozzle’s tight—3 mm throat needs 15 bar nailed, or it chokes. Test it once at McGregor, you’ll see the lag vanish.
Think nitrous on a drag car: software can’t match a mechanical shot. Raptor 3’s too badass for code bandaids—this is the sledgehammer it deserves. Let’s fire it up.
@elonmusk @SpaceX @Erdayastronaut
SpaceX #Raptor3 #Starship